Vitamin D
Vitamin D is a vitamin that "includes both cholecalciferols and ergocalciferols, which have the common effect of preventing or curing rickets in animals. It can also be viewed as a hormone since it can be formed in skin by action of ultraviolet rays upon the precursors, 7-dehydrocholesterol and ergosterol, and acts on vitamin d receptors to regulate calcium in opposition to parathyroid hormone."[1]
Biochemistry
Ergocalciferols (vitamin D2) is formed in plans. Ergocalciferols are "derivatives of ergosterol formed by ultraviolet rays breaking of the C9-C10 bond. They differ from cholecalciferol in having a double bond between C22 and C23 and a methyl group at C24."[2]
Cholecalciferol (vitamin D3) is formed in the skin from 7-dehydrocholesterol by sunlight. Cholecalciferon is a "derivative of 7-dehydroxycholesterol formed by ultraviolet rays breaking of the C9-C10 bond. It differs from ergocalciferol in having a single bond between C22 and C23 and lacking a methyl group at C24."[3]
Vitamin D2 and vitamin D3 are of equal potency.[4]
Vitamin D3 is hydroxylated in the liver at the 25 position.[4] Next is calcitriol (1,25-Dihydroxyvitamin D3). Calcitriol is the "physiologically active form of vitamin D. It is formed primarily in the kidney by enzymatic hydroxylation of 25-hydroxycholecalciferol (calcifediol). Its production is stimulated by low blood calcium levels and parathyroid hormone. Calcitriol increases intestinal absorption of calcium and phosphorus, and in concert with parathyroid hormone increases bone resorption."[5]
Deficiency
Low levels of vitamin D are common in medical inpatients[6], some populations of patients with widespread musculoskeletal pain like fibromyalgia[7].
References
- ↑ Anonymous (2024), Vitamin D (English). Medical Subject Headings. U.S. National Library of Medicine.
- ↑ Anonymous (2024), Ergocalciferols (English). Medical Subject Headings. U.S. National Library of Medicine.
- ↑ Anonymous (2024), Cholecalciferol (English). Medical Subject Headings. U.S. National Library of Medicine.
- ↑ 4.0 4.1 Harper, Harold W.; Murray, Robert F. (2000). “Structure and Function of the Lipid-Soluble Vitamins”, Harper's Biochemistry. Norwalk, CT: Appleton & Lange, 645. ISBN 0-8385-3684-0.
- ↑ Anonymous (2024), Calcitriol (English). Medical Subject Headings. U.S. National Library of Medicine.
- ↑ Thomas MK, Lloyd-Jones DM, Thadhani RI, et al (1998). "Hypovitaminosis D in medical inpatients". N. Engl. J. Med. 338 (12): 777–83. PMID 9504937. [e]
- ↑ Plotnikoff GA, Quigley JM (2003). "Prevalence of severe hypovitaminosis D in patients with persistent, nonspecific musculoskeletal pain". Mayo Clin. Proc. 78 (12): 1463–70. PMID 14661675. [e]